Telephone-exchange system



H. P. CLAUSEN AND C. L. GOODRUM.

TELEPHONE EXCHANGE SYSTEM. A PPLICATION rurn JULY 11. 1919.

Patented Mar. 15, 1921.

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hen/y PCma/aen Char/e6 L Gaodzum UNITED STATES PATENT OFFICE.

HENRY P. GLA'USEN, OF MOUNT VERNON, AND CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHAN GE SYSTEM.

Specification of Letters Patent.

Patented Mar. 15, 1921.

7 '0 all whom it may concern:

Be it known that we, HENRY P. CLAUSEN and CHARLES L. GOODRUM, citizens of the United States, residing at Mount Vernon, in the county of Westchester and State of New York, and at New York, in the county of New York and State of New York, respectivel have invented certain new and useful mprovements in Tele hone Exchange Systems, of which the fol owing is a full, clear, concise, and exact description.

This invention relates to improvements in telephone exchange systems and has particular reference to means for operating the switches therefor.

In automatic s stems, the most commonly employed metho of operating switches has been by direct current impulses transmitted over portions of a line, other portions of which are opaque to such impulses by reason of the use of condensers or other existing conditions.

An object of this invention is to employ alternating current for operating a switc to select telephone lines and also to control the release of said switch.

A feature of the invention is to connect to a line an alternating current generator of a frequenc sufficiently low to be inaudible in a telep one receiver and operate said generator, when the line is taken, to transmit an alternating current thereover which will actuate an electromagnetic device to control the release of a switch.

Another feature is the provision of a second alternating current generator of a higher frequency which may or may not be audible in a telephone receiver an which, when connected to a line in res onse to interruptions therein, will controi the operation of a switch in the usual manner.

The inventive idea involved is capable of receivin a variety of expressions, some of which, or the purpose of illustrating the invention, are shown in the accompanying drawing; but it is to be expressly understood that said drawing is employed merely for the pur ose of facilitating the description of the invention as a whole, and not to define the limits thereof, reference being had to the appended claims for this purpose.

In the drawing, Figure 1 is a diagrammatic view of a circuit arrangement showing the application of the invention to a metallic circuit. Fig. 2 is a similar view illustrating the application of the invention to a phantom circuit, only so much of the invention being shown as is necessary for an understanding thereof.

The invention permits of the operation of Switches over a circuit containing condensers or various conditions which render the circuit opaque to direct current.

It is believed that the invention will be fully understood from the following detailed description of the operation.

When a subscriber at substation 1 initiates a call by removing his receiver from its switchhook, a line or finder switch will be operated, in a manner well known in the art, to connect the calling trunk line to an idle trunk. Line relay 2 will be energized over a circuit extending from grounded battery, right winding of said relay, winding 3 of a repeating coil, wiper of the line or finder switch, substation apparatus 1, the other wiper of the line or finder switch winding 4 of said repeating coil and left winding of relay 2 to ground. In energizing, relay 2 establishes a circuit for slow-torelease relay 5 extending from ground through the front contact and outermost armature of relay 2 and winding of relay 5 to grounded battery. This relay, in attracting its right armature, connects a low frequency current generator 6 to the sides 7 and 8 of the trunk. This alternating current will pass through the condensers 9 and 10 and winding of relay 11 to energize the same. Energization of relay 11 operates to seize a selector switch 13 having primary and secondary stepping movements. By attracting its ri ht armature relay 11 closes a circuit for re ay 12 of selector switch 13, which circuit extends from grounded battery, through right winding of relay 12, back contact and upper armature of cutofi' relay 14, winding 15 of a repeating coil, back contact and armature of relay 16, right armature and front contact of relay 11, winding 17 of said repeating coil, inner lower armature and back contact of relay 14 and left winding of relay 12 to ground. Relay l2 attracts ltS armature and establishes a circuit for slow-to-release relay 18. When relay 11 attracts its left armature, a

busy test will be provided for switch 13 over a circuit extending from ground at the left armature of relay 11, conductor 19, offnormal switch 28 when the sameis closed upon the first step of the switch, back contact and outer armature of magnet 27 to brush 25. It will be noted that when relay 2 is energized, by attracting its middle and innermost armatures, it disconnects a high frequency current generator 20 from the telephone line.

Switch 13 is now in condition to receive impulses transmitted from substation 1 and in response to each of these impulses, line relay 2 is deenergized and connects the high frequency generator 20 to the sides 7 and 8 of the line. Current from this generator passes through condensers 9 and 10 and the winding of relay 16 which is tuned to respond only tohigh frequencycurrents in any manner well known in the art. Upon each application of the high frequency alternating current to the line in response to the interruptions of line relay 2, relay 16 is energized thus interrupting the circuit for line relay 12 which, in releasing its arma- .ture, establishes a circuit for the primary stepping magnet 21 of switch 13 extending from grounded battery, through the winding of said magnet, winding of the slow-torelease relay 22, front contact and armature of relay 18, lowermost armature and back contact of relay 14, back contact and armature of relay 12 to ground. Relay 22 becomes energized in this circuit and, together with relay 18, maintains its armature attracted throughout the transmission ofimpulses. Magnet 21 operates to step brushes 23, 24; and 25 of switch 13 in a group selecting movement. When relay 22 is energized, a circuit is established for test relay 26 extending from grounded battery, winding of said relay and armature and front contact of relay 22 to ground. Relay 26 locks up over a circuit from grounded battery through its winding, front contact and armature, outer armature and back contact of secondary stepping magnet 27, ofi-normal contact 28 which is closedupon the first primary step of the switch, conductor 19, and left-hand armature andfront contact of relay 11 to, ground. At thetermination of the series of impulses, line relay 2 maintains its armatures attracted and thus permanently disconnects the generator 20 from the line with the result that stepping relay 16 will remain deenergized to maintain closed the previously described circuit for the line relay 12. This relay also main.- tains its armature attracted and opens the circuit through the slow-to-release relay 22 which, after an interval, releases.

A-self-interrupting circuit isthen established for the secondary stepping magnet 27 extending from grounded battery, winding,

inner armature and back contact of said magnet, back contact and armature of relay 22, front contact and armature of relay 26, outer armature and back contact of magnet 27, off-normal contact 28, conductor 19 and left-hand armature and front contact of relay 11 to ground. Magnet 27 now op erates to step brushes of switch 13 over the terminals of the selected group to hunt for an idle trunk therein. The busycondition of trunks in this group of terminals is denoted by ground upon test termi'nal29 and when brush 25 vengages the terminal'of a busy trunk, the locking circuit for test relay 26 will be maintained through brush 25 and terminal 29 of said trunk to ground. Magnet 27 will therefore continue to step the brushes of the switch over terminals of busy trunks until an idle one is reached. At this time, brush 25, no longer finding ground,

opens a locking circuit for relay 26 and thus tending from grounded battery, winding of said relay, back contact and armature of relay 26, outer armature and back contact of magnet 27, off-normal contact 28, conductor 19 and left-hand armature and front contact of relay 11, to ground. This circuit is maintained until the deenergizationofrelay 11 caused by the retraction of the righthand armature of relay 5. By attracting its armatures, relay 141 extends the calling line to the next succeeding switch which may be operated in the same manner as described in connection with switch 13. Relay 14 also permanently opens thecircuit for relay 12 which, in releasing, causes the deenergization of slow-to-release relay '18.

At the termination of the conversation be tween a calling and a called subscriber, release'of the switch 13 is controlled bythe calling subscriber, When the receiver is re placed upon its switchhook at substation 1, line relay 2 deenergi'zes and opens the circuit for slow-to-release relay 5. This relay then, in turn, releases its armature to disconnect the low frequency current generator from the telephone line and thus cause the release of relay 11. 'By retracting its left armature, this relay opens the holdin circuit of relay 14 which thenreleases. circuit is then established for release magnet 30 extending from grounded battery, winding of said magnet, spring 31 of offnormalv contact 28, back contact and armature of relay 18, lowermost armature and back contact of relay 141, back contact and armature of relay 12 to .ground. Magnet 30 operates to restore the brushes of the switch to normal position whereupon off-normal contact 28 is also restored and the energizing circuit of magnet 30 permanently opened. The switch is now in position for another operation.

In Fig. 2, the invention is shown as applied to a phantom circuit and it is believed that a brief reference to the disclosure in this figure will enable those skilled in the art to understand the invention when considered in connection with the foregoing description.

In this figure, 6' indicates the low frequency alternating current generator which is connected to the line when slow-to-release relay 5' is energized in response to the operation of the line relay 2. The connection of the generator 6 to the line causes the energization of relay 11', the operation of which is precisely the same as that of relay 11. In response to interruptions in the line circuit caused by impulses transmitted, relay 2' deenergizes to connect the high frequency alternatin current generator 20' to the line where y stepping relay 16 is operated to control the stepping of a switch (not shown} similar to switch 13.

What is c aimed is:

1 In a telephone system, an automatic switch, means for operating said switch, a release control magnet and alternating current means for maintaining said magnet ener%zed during the operation of said switc 2. In a telephone system, an automatic switch, a release control magnet one source of alternating current means or ener 'zmg said magnet to permit of the operation of said switch, and another source of alternating current means for causing the operation of said switch.

3. In a telephone system, a telephone line, an automatic switch, means actuated upon the seizure of said line for transmitting an alternating current thereover, release control means responsive to said current, and alternating current controlled means for operating said switch.

4. In a telephone system, an automatic switch, means for operating said switch means for controlling the release of sai switch, and sources of alternatin current of different frequencies, one of w ich controls the operation of said operating means, and the other the operation of said releasing means.

5. In a telephone system, a telephone line, an automatic switch, means actuated upon the seizure of said line for transmitting an alternating current thereover, means responsive to said current for controlling the release of said switch, means responsive to impulses for transmitting another alternating current over said line, and means responsive to the last named alternating current for operating said switch.

6. In a telephone system, a telephone line, an automatic switch, means actuated upon the seizure of said line for transmitting an alternating current thereover, a relay responsive to said current for controlling the release of said switch, a relay responsive to impulses for transmitting another alternating current over said line, and means responsive to the last named alternating current for operating said switch.

7. In a telephone system, telephone lines, an automatic switch, a relay for controlling the setting of said switch, a relay for controlling the release of said switch, sources of alternating current of different frequencies, means for extending a calling line to said switch and for applying alternating current from one of said sources to said release relay to maintain the same operated, and manually controlled means for applying impulses of alternating current from the other source of the first named relay for controlling the setting of said switch on one of said lines.

In witness whereof, we hereunto subscribe our names this 9th da of Jul A. D. 1919.

HENR P. CL iJsEN. CHARLES L. GOODRUM. 

